The present invention relates to a protein containing a serum albumin domain. The present invention more specifically relates to a protein having an enhanced functional activity or activities selected from among the various functional activities of the domains of serum albumin including antibacterial activity, antioxidative effect, inflammation inhibitory effect, in vivo substance transporting action, and enzymatic activity. Such a protein is provided by producing proteins of various combinations of serum albumin domains by gene recombinant technology.